/*
 * mppe.h - Definitions for MPPE
 *
 * Copyright (c) 2008 Paul Mackerras. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The name(s) of the authors of this software must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission.
 *
 * 4. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by Paul Mackerras
 *     <paulus@samba.org>".
 *
 * THE AUTHORS OF THIS SOFTWARE DISCLAIM ALL WARRANTIES WITH REGARD TO
 * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS, IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
 * SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
 * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include "netif/ppp/ppp_opts.h"
#if PPP_SUPPORT && MPPE_SUPPORT  /* don't build if not configured for use in lwipopts.h */

#ifndef MPPE_H
#define MPPE_H

#include "netif/ppp/pppcrypt.h"

#ifdef __cplusplus
extern "C" {
#endif

#define MPPE_PAD        4   /* MPPE growth per frame */
#define MPPE_MAX_KEY_LEN    16  /* largest key length (128-bit) */

/* option bits for ccp_options.mppe */
#define MPPE_OPT_40     0x01    /* 40 bit */
#define MPPE_OPT_128        0x02    /* 128 bit */
#define MPPE_OPT_STATEFUL   0x04    /* stateful mode */
/* unsupported opts */
#define MPPE_OPT_56     0x08    /* 56 bit */
#define MPPE_OPT_MPPC       0x10    /* MPPC compression */
#define MPPE_OPT_D      0x20    /* Unknown */
#define MPPE_OPT_UNSUPPORTED (MPPE_OPT_56|MPPE_OPT_MPPC|MPPE_OPT_D)
#define MPPE_OPT_UNKNOWN    0x40    /* Bits !defined in RFC 3078 were set */

/*
 * This is not nice ... the alternative is a bitfield struct though.
 * And unfortunately, we cannot share the same bits for the option
 * names above since C and H are the same bit.  We could do a u_int32
 * but then we have to do a lwip_htonl() all the time and/or we still need
 * to know which octet is which.
 */
#define MPPE_C_BIT      0x01    /* MPPC */
#define MPPE_D_BIT      0x10    /* Obsolete, usage unknown */
#define MPPE_L_BIT      0x20    /* 40-bit */
#define MPPE_S_BIT      0x40    /* 128-bit */
#define MPPE_M_BIT      0x80    /* 56-bit, not supported */
#define MPPE_H_BIT      0x01    /* Stateless (in a different byte) */

/* Does not include H bit; used for least significant octet only. */
#define MPPE_ALL_BITS (MPPE_D_BIT|MPPE_L_BIT|MPPE_S_BIT|MPPE_M_BIT|MPPE_H_BIT)

/* Build a CI from mppe opts (see RFC 3078) */
#define MPPE_OPTS_TO_CI(opts, ci)       \
    do {                    \
    u_char *ptr = ci; /* u_char[4] */   \
                        \
    /* H bit */             \
    if (opts & MPPE_OPT_STATEFUL)       \
        *ptr++ = 0x0;           \
    else                    \
        *ptr++ = MPPE_H_BIT;        \
    *ptr++ = 0;             \
    *ptr++ = 0;             \
                        \
    /* S,L bits */              \
    *ptr = 0;               \
    if (opts & MPPE_OPT_128)        \
        *ptr |= MPPE_S_BIT;         \
    if (opts & MPPE_OPT_40)         \
        *ptr |= MPPE_L_BIT;         \
    /* M,D,C bits not supported */      \
    } while (/* CONSTCOND */ 0)

/* The reverse of the above */
#define MPPE_CI_TO_OPTS(ci, opts)       \
    do {                    \
    const u_char *ptr = ci; /* u_char[4] */ \
                        \
    opts = 0;               \
                        \
    /* H bit */             \
    if (!(ptr[0] & MPPE_H_BIT))     \
        opts |= MPPE_OPT_STATEFUL;      \
                        \
    /* S,L bits */              \
    if (ptr[3] & MPPE_S_BIT)        \
        opts |= MPPE_OPT_128;       \
    if (ptr[3] & MPPE_L_BIT)        \
        opts |= MPPE_OPT_40;        \
                        \
    /* M,D,C bits */            \
    if (ptr[3] & MPPE_M_BIT)        \
        opts |= MPPE_OPT_56;        \
    if (ptr[3] & MPPE_D_BIT)        \
        opts |= MPPE_OPT_D;         \
    if (ptr[3] & MPPE_C_BIT)        \
        opts |= MPPE_OPT_MPPC;      \
                        \
    /* Other bits */            \
    if (ptr[0] & ~MPPE_H_BIT)       \
        opts |= MPPE_OPT_UNKNOWN;       \
    if (ptr[1] || ptr[2])           \
        opts |= MPPE_OPT_UNKNOWN;       \
    if (ptr[3] & ~MPPE_ALL_BITS)        \
        opts |= MPPE_OPT_UNKNOWN;       \
    } while (/* CONSTCOND */ 0)

/* Shared MPPE padding between MSCHAP and MPPE */
#define SHA1_PAD_SIZE 40

static const u8_t mppe_sha1_pad1[SHA1_PAD_SIZE] = {
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
};
static const u8_t mppe_sha1_pad2[SHA1_PAD_SIZE] = {
    0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2,
    0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2,
    0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2,
    0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2
};

/*
 * State for an MPPE (de)compressor.
 */
typedef struct ppp_mppe_state {
    lwip_arc4_context arc4;
    u8_t master_key[MPPE_MAX_KEY_LEN];
    u8_t session_key[MPPE_MAX_KEY_LEN];
    u8_t keylen;                /* key length in bytes */
    /* NB: 128-bit == 16, 40-bit == 8!
     * If we want to support 56-bit, the unit has to change to bits
     */
    u8_t bits;                  /* MPPE control bits */
    u16_t ccount;               /* 12-bit coherency count (seqno)  */
    u16_t sanity_errors;        /* take down LCP if too many */
    unsigned int stateful  : 1; /* stateful mode flag */
    unsigned int discard   : 1; /* stateful mode packet loss flag */
} ppp_mppe_state;

void mppe_set_key(ppp_pcb* pcb, ppp_mppe_state* state, u8_t* key);
void mppe_init(ppp_pcb* pcb, ppp_mppe_state* state, u8_t options);
void mppe_comp_reset(ppp_pcb* pcb, ppp_mppe_state* state);
err_t mppe_compress(ppp_pcb* pcb, ppp_mppe_state* state, struct pbuf** pb, u16_t protocol);
void mppe_decomp_reset(ppp_pcb* pcb, ppp_mppe_state* state);
err_t mppe_decompress(ppp_pcb* pcb, ppp_mppe_state* state, struct pbuf** pb);

#ifdef __cplusplus
}
#endif

#endif /* MPPE_H */
#endif /* PPP_SUPPORT && MPPE_SUPPORT */
